Several documents are cited throughout the text of this specification. Each of the documents herein (including any manufacturer's specifications, instructions etc.) are hereby incorporated by reference; however, there is no admission that any document cited is indeed prior art of the present invention.
The human eye consists of a composite lens system [T. Hellmuth Sensors Update 3(1), 289-223(2001)]. When light enters the eye, the cornea is the first lens encountered and has a large refractive power (typically 54-59 dioptry, refractive index 1.38). Behind the diaphragm or iris the light is refracted by a second lens (refractive index 1.41) with variable dioptry in view of accommodating [T. Missotten et al., Journal of Cataract and Refractive Surgery 30(10), 2084-2087 (2004)], i.e. finely adjusting the dioptric strength of the lens (typically between 0 and 4 dioptry) in order to focus the view on an object at given distance and thus getting a sharp image on the retina, which collects the light that leaves the second lens and reaches the retina via the vitreous humor (refractive index 1.34). In natural circumstances the strength of the second lens is adjusted by shape changes induced by (de-) contractions of the ciliary muscle around the ciliary muscle. The state of the ciliary muscle is controlled by the brain via the muscle nerves. The motoric part of the brain is hereby continuously receiving signals via the optic nerve front the visual cortex in order to steer the ciliary muscle so that sharp vision is obtained for the object under inspection. Since the system acts as a closed, iterative feedback loop, the system ensures sharp vision at every time provided that the required refractive lens power lies within the dynamic range of the ciliary muscle-lens system, and provided sufficient time is provided to process the visual information and adjust the ciliary muscle.
As the age of a person increases, typically starting from 45 years and above, the fibers of the accommodating lens lose their elasticity so that the dioptric range is reduced, inhibiting the eye to focus on objects at short distances, in spite of a perfectly functioning (typically during the whole lifetime of a person) ciliary muscle. Typically people solve this problem by using glasses or contact lenses with positive dioptry when necessary.
In the case of cataract disease, the variable lens becomes milky, leading to a reduction transparency and blurred vision. A partial cure of this problem is achieved by replacing the natural lens by an artificial one, whose dioptry is chosen (lenses with strengths between −10 and +35 dioptry are commercially available) that the eye lens assembly in rest gives a sharp focus at very long distances. A standard artificial lens is monofocal and accommodation is no longer possible. Glasses are necessary to provide sharp vision at intermediate distances, in particular at reading distance. Multifocal artificial lenses also exist, providing simultaneous sharp vision at multiple distances. The brain is then subconsciously ‘choosing’ which image information out of the composite multifocal image it is processing. However, since at any time a multifocal lens is projecting images from different focal distances on the retina, every sharp object (in particular in a dark environment in the presence of strong light sources) is surrounded by a blurred halo or glare. In addition, the distribution by a multifocal on multiple focal points leads to a contrast reduction.
Ideal restoration of the accommodative power of a human eye suggests the design of a self-adjusting variable lens. This concept has been shown by automatically accommodating spectacles [G. Li, D. L. Mathine, et al. Proceedings of the National Academy of Sciences of the United States of America, PNAS published online Apr. 5, 2006; doi; 10.1073/pnas.0600850103], in which the dioptric power of the glasses was electro-optically adjusted (cfr autofocus of a digital camera), depending on the conscious choice of the user. This solution is obviously not equivalent to the truly ideal natural way of vision, i.e. the automatic self-accommodating intraocular lens, which sub-consciously self-adjusts to get a sharp image of the object under inspection. Also, the refractive power of liquid crystal based electro-optic spectacle lenses is polarization dependent, leading to partial image blur and halo and glare effects.
Also progress has been made on intraocular solutions for a self-adapting lens that makes use to a maximum extent of the naturally available anatomical tools. A possible system contains an intraocular lens that is mounted such that its shape (or position) and thus refractive power (in combination with a second intra-ocular lens), is mechanically determined by the state of the ciliary muscle. In this way the functionality of the natural eye lens is restored. However, it turns out that this system is problematic, because typically for most patients the elasticity of the lens diaphragm is distorted, thus deteriorating the mechanical control of the adaptive lens by the ciliary muscle.
Related to the control of the refractive power of the eye, some techniques exist to detect the state of the eye. Opthalmological apparatus exist to determine the width of the iris, to visualize the ciliary muscle, and to determine the refractive power of the eye lens assembly. These techniques are based on the optical access via the iris, and on ultrasonic echography. A solution is by determining the eye ball pressure via inserted electrodes. However, no techniques have been proposed to electronically monitor the state of the ciliary muscle. Neither have there been proposals for building and energetically maintaining stand-alone electronic circuitry in the eye ball.
There is thus a need in the art for an intra-ocular lens whose refractive power is controlled in a seamless manner by a signal that is representative for the state of the ciliary muscle, or other muscular signals, or other positional markers that reflect to which direction the visual cortex wants to change the eye lens dioptry, and for the detection of that signal. There is also a need for a wireless method to continuously or frequently supply energy to the intraocular device from a device located out of the human body, and for a small intraocular device that receives, stores and releases this energy.
The present invention comprises an intraocular lens with electro-optically controlled refractive power that can be surgically placed. By making use of a dual lens assembly and a hybrid lens design that makes use of electronically controlled liquid crystal alignment on one hand and a curved (e.g. concave) lens shape on the other hand, the refractive power of intra-optic lens is made polarization independent, resulting in optimum focus for near to 100%, for instance more than 98%, preferably more than 99%, of the incident light, with minimum light loss due to reflection and absorption. This solves the glare and halo problems in the current state of the art. The curved lens shape allows the use of easy to produce uniform electrodes. Without voltage applied over the electrodes of the first lens (“lens L1”), the liquid crystal is aligned in a planar way due to the presence of a thin, transparent aligning layer on top of the transparent electrode. When the voltage over the electrodes is increased, the liquid crystal alignment tends more and more to homeotropic alignment. As a result, the effective refractive index of the liquid crystal layer for one of the two polarization components (“component P1”) of the incident light is monotonously changed with the applied voltage. In combination with the curvature of one of the interlaces between the liquid crystal with the surrounding material, the change of refractive index results in a change of dioptric strength of the assembly for this polarization component. The dioptric strength of the other (orthogonal) polarization component (“component P2”) is not affected by the voltage changes over lens L1. The second liquid crystal lens (“lens L2”) assembly is placed in series with the first one. The planar alignment direction of the second lens is chosen perpendicular to the planar alignment of the first lens. As a consequence, lens L2 affects the dioptric strength for P2 and not for P1. Thus, together, L1 controls the dioptric strength of P1 and L2 controls the dioptric strength of P2. In this way, the dioptric strength of 100% of the light is controlled.
The steering signal for the refractive power control used in this invention is based on the electromagnetically detected position of a marker, which is placed in such a position so that this position is representative for the direction in which the visual cortex wants to change the dioptric strength in order to get a sharp image. In other words, in an embodiment of present invention an electromagnetically detected position of a marker, which is representative for an optic nerve signal from the visual cortex generated from neuronal processed spatiotemporal features and to change the dioptric strength in order to get a sharp image, is translated in the system or device of present invention into a time-varying voltage or current that conveys information that is a steering signal to control the refractive power of the lens. The electronic detection system or parts or elements of the electronic detection zone are preferably located in the peripheral zone of the artificial intraoptic lens, out of the transparent zone which transmits the light from the outside world to the retina.
The principle of detection is based on the monotonic relation between one or more of the marker positional coordinates, and the electric impedance of an inductive element comprised in a detector system, consisting for instance of at least one inductive coil or a wired inductive material or deposited metal structure on a printed circuit board, or of a Hall sensor located in the detection system.
On one hand the electric impedance of the inductive element or elements, for instance the detection coil, is electronically monitored by placing the inductive element for instance the coil in an appropriate electronic circuit (e.g. an amplitude (AM) or frequency (FM) detection circuit whose details are described further on). On the other hand, the electromagnetic field, around of the inductive elements or elements, for instance around the coil, and thus the inductive elements' for instance coil's electric impedance, is influenced by the electromagnetic properties of its environment, and in particular on the electric and magnetic properties of the marker, and on the marker position. Thus, changes in the marker's position, are reflected in changes in the electronic detector signal, and the other way around. The electric and magnetic properties, as well as the placement of the marker, are optimized in order to maximize the sensitivity of the impedance based signal to the marker's positional changes.
A particular specific embodiment of present invention concerns sensing the electric impedance of a detection coil whereby the coil is electronically monitored by an electronic circuit (e.g. an amplitude (AM) or frequency (FM) detection circuit whose details are described further on). Hereby the. electromagnetic field around of the coil, and thus the coil's electric impedance, is influenced by the electromagnetic properties of its environment, and in particular by spatiotemporal features of a marker that has an electrical conductivity or magnetic susceptibility different from the surrounding medium.
The above can be integrated in various schemes or embodiments.
In a first scheme embodying the present invention, the marker is surgically placed so that it is comprised in or is on the ciliary muscle, or near to it, in the zonular fiber connection zone between the ciliary muscle and the lens body. The ciliary muscle or the ring of striated smooth muscle in the eye's middle layer (vascular layer) that controls lens accommodation and that enabling changes in lens shape for light focusing. A marker placed on such ciliary muscle will change in spatiotemporal features during visual cortex instructed lens accommodation. A marker position near to the ciliary muscle is in the meaning that it is in or on a surrounding tissue so that during visual cortex instructed lens accommodation the spatiotemporal features are modified so that they are representative for the state of the ciliary muscle, or other muscular signals, or other positional markers that reflect to which direction the visual cortex wants to change the eye lens dioptry, and for the detection of that signal. In this way, (de)contractions of the ciliary muscle (which are representative for the focal changes desired by the visual cortex) result in changes of the relative position of the marker with respect to the detection coil. Hence, the electronic detection coil signal can be used as a measure of the ciliary muscle contraction and of thus of the intention of the visual cortex, in order to adjust, via an electronic interface between the detection system and the electro-optic system, the refractive power of the intraoptic lens. This mechanism restores the natural feedback system of focusing on objects whose position is varying over a wide range of distances, where the visual cortex plays the role of monitoring the sharpness of the image, and adjusting accordingly the refractive power of the eye lens.
In a second scheme or embodiment of the invention, the electronic detection system, in total of in part or its core, is still located in the peripheral zone of the artificial intraoptic lens, preferably out of the transparent zone which transmits the light from the outside world to the retina. However, the marker is surgically (subcutaneously) or externally placed (attached to the skin) in the region between both eyes, or even elsewhere on the head, not too far away from the eye ball in which the detection circuitry is residing, e.g. subcutaneously or attached to the skin on the temple of the person's head, or inside of spectacles. Unlike in the first scheme, in this case the relative position of the marker with respect to the inductive element, for instance the detection coil, is quasi independent of the state of the ciliary muscle. For this second system of detection, we make use of the following, alternative mechanism. When a person wants to focus on a nearby object, then, besides a ciliary muscle contraction, there is also a visual cortex controlled turning-in of the eye balls towards the central axis in the vision direction. The degree of turning-in is proportional with the intended degree of focusing. The turning-in also goes along with a change of relative position between the intraocular detection system, which is inside of the turning-in eye ball and thus following the eye movement, and the marker, which has a fixed position with respect to the person's head. Therefore, the impedance of the inductive element, for instance the detection coil which is electronically determined by the detection circuit, and which is sensing the distance between marker (fixed position) and eye ball (position dependent on the distance of the object of interest), is a measure for the intention of the visual cortex in terms of refractive power. Thus, as in the first scheme, this signal can be used to close the adaptive feedback loop that controls the dioptric strength of the eye lens in order to keep focused on objects of interest.
In a third scheme which is an embodiment of the invention, one or more markers and/or detection systems are placed in both eyes. The turning-in of the eyes then also is reflected in the relative positions between markers and detection systems, so that the derived impedance signals can be used for dioptric control in the electro-optic circuitry. In the following, the electronic scheme to measure the impedance (or changes of the impedance) of the inductive element is described in more detail e.g. the detection coil, and its geometry and placement. In this invention, the impedance (changes) is detected by putting the inductive element, for instance the coil (inductance) in an electric oscillator circuit (e.g. a Colpitts oscillator). The resonance frequency of this circuit then monotonically depends on the inductance (and thus impedance) of the inductive element, e.g. the coil. This resonance frequency can then be derived using an FM detection system, e.g. a phase locked loop circuit (PLL) or frequency to voltage converter (PVC). Alternatively, the frequency of the oscillator circuit can be forced, such that changes of the impedance are transformed into amplitude changes of the oscillator voltage, so that classical electronic circuits for AM demodulation can be used, e.g. lock-in amplifier type of circuits.
Given the need for optical transmission in the middle part of the lens implant, only the peripheral zone of the lens body can be used to put electronic circuitry. This is depicted in the figures. Different schemes are possible for the geometry and positioning of the coil, e.g. the coil can be planar or cylindrical, it can be parallel with or perpendicular to the equator plane, and a dual coil with or without differential detection can be used in order to enhance the sensitivity and directivity of the detection or changes in the environment, and the selectivity to detect the marker (and not possible other motions of electromagnetically active objects in the neighborhood).
The material for the marker should be such that it has a maximum impact on the electromagnetic field, and thus electric impedance of the inductive element, for instance the coil, e.g. the markers are ferromagnetic and/or paramagnetic and or electrically conducting.
In an alternative scheme of this invention, instead of inductive detection, the position of a para- or ferromagnetic marker can be detected by a Hall probe that monitors the strength of the magnetic field of the marker, and thus its positional changes. This can be replaced in above-mentioned embodiments wherein in such case the markers are para- and/or ferromagnetic marker and their position or spatiotemporal features are detected by such Hall probe.
In yet another alternative embodiment of present invention, the marker is an inductive element (e.g. coil), and the detection is based on the principle of mutual induction between this element and the intraoptic detection circuit. Also here, positional changes of the marker coil are reflected in electronic signal changes in the detection circuit. The previous embodiments mentioned in this application can be adapted by this scheme. This invention also generally solves related issues of biometric sensing of the state of muscles.
In an alternative embodiment of present invention at least one Hall sensor detects the position of the ciliary muscle marker tag.
In another alternative, the incentive of the visual cortex to adjust the dioptric strength of the eye lens is determined by inductively sensing (or sensing via a Hall sensor) within the intraocular lens circuitry the relative distance of the eyeball to a metal piece between the eyes, and thus the angular orientation of the eye ball, which is a known measure for the distance to which a person wants to focus his or her view.
In a particular embodiment the intra-ocular and biocompatible miniaturized electro-optic device is supplied of energy from a device out of the body, in particular by a (near infrared, invisible) light transmitter in front of the eye to a solar cell on the eye lens, and by inductive electromagnetic transmission of AC electromagnetic energy from a coil in front of or around the eye or person's head (e.g. in the person's sleeping pillow) to a coil on the intraocular lens.
In a particular embodiment the intra-ocular and biocompatible miniaturized electro-optic device is supplied of energy from a device out of the body, in particular by a light transmitter, for instance by a near infrared, invisible, light transmitter in front of the eye to a solar cell on the eye lens, and by inductive electromagnetic transmission of AC electromagnetic energy from a coil in front of or around the eye to a coil on the intraocular lens.
In a particular embodiment the lens is a lens assembly of two plane parallel lenses (having opposite surfaces exactly plane and parallel) with a radial refractive index gradient, depending on optical thickness of the liquid crystal (LC) layer between two opposite lenses the focal distance of this assembly will vary.
In yet another particular embodiment the lens is a curved lens with a patterned hole electrode for an electrical field gradient, and thus a gradient in refractive index, which in turn results in voltage controllable refractive power.